1. Field of the Invention
This invention relates broadly to apparatus for wrapping spherical objects. More particularly, this invention relates to an apparatus for wrapping tape about a spherical aerial firework shell.
2. State of the Art
Aerial firework shells generally include a shell portion containing an arrangement of bursting charge and stars, and a fuse extending from outside the shell to the interior thereof to ignite the bursting charge and stars. The stars are pellets which burn in color and provide the spectacular display of the firework. The bursting charge is generally black powder and provides the force which disperses the stars when the firework shell is shot.
There are generally two types of aerial firework shells: cylinder shells and spherical shells. Cylinder shells are originally Italian in design and contain the bursting charge and stars in a cylindrical casing. Spherical shells are originally Chinese in design and contain the bursting charge and stars in a spherical casing. Spherical shells generally come in one of several standard sizes, diameters of six inches, eight inches, ten inches, twelve inches, and sixteen inches, although other sizes can be constructed. It is the spherical shell which is most common at large professional firework displays, such as seen on the fourth of July.
In the prior art, spherical firework shells are made entirely by hand. Two hemispherical shell portions are each filled with bursting charge and stars and then brought together to form a sphere. A single piece of tape is manually applied to the sphere to temporarily maintain the integrity of the sphere. One of the shell portions is provided with a fuses which extends from outside the portion to the interior of the shell adjacent the bursting charge. The sphere is then evenly wrapped in individual strips of kraft paper, each generally one to two inches wide and having a length which is substantially the diameter of the sphere. The kraft paper is applied to the sphere using a paste, in a manner similar to papier-machxc3xa9. The paper wrapping integrates the shell and provides a casing having the necessary structural integrity to permit the shell to be shot from a cannon and not allow the shell to explode until the lit fuse extending between the exterior of the casing and the interior black powder reaches the black powder. To that point, when the shell is wrapped, care is taken to wrap around the fuse, and not cover or otherwise inhibit the function of the fuse. The wrapping of the casing must be very evenly applied in thickness for the shell to explode in a substantially uniform spherical display, as desired. In order that the pasted kraft paper strips should have the required structural integrity, typically forty layers or more of the paper strips are provided about the shell to form a sufficiently strong outer casing.
This paper wrapping process is very labor intensive, requiring hours of manual work for small shells, and days of work for the largest shells. Moreover, the wrapping can be extremely dangerous as the bursting charge is highly combustible. Unfortunately, due to the labor costs, the job of firework manufacture has typically fallen on women and children working under unsafe conditions in economically depressed areas. Widespread disregard for industrial safety and lax enforcement of existing laws lead to frequent deadly accidents in such areas. Recent deaths in China have highlighted the problem. On Mar. 20, 2001, two children were killed in rural China in an explosion at an illegal fireworks factory. Just days before, on Mar. 7, 2001 an explosion at a school in China where children were forced to make fireworks in classrooms killed at least 42 people, mostly children.
It is therefore an object of the invention to provide a spherical firework shell wrapping system which minimizes human contact with the shell.
It is another object of the invention to provide a system which automatically wraps a spherical firework shell.
It is a further object of the invention to provide a system which evenly wraps a shell of a spherical firework to provide a desirable casing for the firework shell.
It is an additional object of the invention to provide a firework shell wrapping system which is relatively safe to use.
It is also an object of the invention to provide a wrapping system which can evenly wrap spherical objects other than firework shells.
In accord with these objects, which will be discussed in detail below, an apparatus for wrapping fireworks shells is provided and includes a base provided with preferably three support rollers configured to support a spherical firework shell thereon, stepper motors coupled to two of the rollers, a computer coupled to the stepper motors to control the movement of the stepper motors and thereby control the angular rotation of the shell on the rollers, and a dispenser assembly which dispenses continuous-feed tape for wrapping the shell and applies and presses the tape to the shell as the shell is rotated on the rollers. The computer instructs the stepper motors to systematically, at times, rotate the rollers at relatively different speeds, such that a shell on the rollers is subjected to angular rotation and the tape is evenly applied to all portions of the shell such that the tape forms a very even casing of the shell. Additional containment rollers are preferably provided to contain a spherical shell as it is rotated on the support rollers.
In order to accommodate different sizes of spherical shells, different apparatus may be particularly configured for specific sizes of shells: the spacing of the rollers and the height of the applying and pressing components of the dispenser assembly are based upon shell size. As an alternative, an embodiment of an adjustable apparatus in which the roller spacing and the height of the applying and pressing components are both adjustable in order to accommodate shells of different sizes in a single apparatus is also provided.
In operation, a shell is initially assembled by hand from two shell half portions, each provided with the bursting charge and stars, into a sphere. A single piece of tape is manually applied to the sphere to temporarily maintain the integrity of the sphere. Thus far, the assembly is performed in the conventional manner with one exception. No fuse is provided in the sphere. Rather, according to an aspect of the invention, at the fuse hole, a small marker such as a magnet is fixed, for example, with a piece of tape.
Then, according to the invention, the spherical shell is provided on the rollers, and tape from the dispenser is contacted with a portion of the sphere and pressed thereto such that it adheres to the shell. The stepper motors are then activated by the computer to rotate the shell in a pattern which applies multiple layers of tape relatively evenly about the shell. The wrapping is considered complete when sufficient tape in a sufficiently even application is present to form the desired casing.
After the shell is wrapped, a suitable device is used to locate the marker for the fuse. For example, if the marker is a magnet, iron filings can be placed on the shell to locate the marker. The casing is then carefully cut at the marker location to remove the marker, expose the fuse hole, and a fuse is fed through the casing and into the shell and sealed with epoxy to complete the firework.
With the apparatus of the invention, the time for wrapping fireworks shells is greatly reduced to minutes, rather than the hours or days of the prior art. Moreover, once started, the apparatus can run substantially unassisted and therefore provides a much safer method of manufacture than the completely handmade method.
It will be further appreciated that the wrapping apparatus can be used to wrap any other spherical object in a manner similarly described with respect to the firework shells.